Painted by Eustache Le Sueur between 1645 and 1648, the decoration of the small cloister of the Paris Charterhouse consisted of thirty pictures illustrating the life of St-Bruno, founder of the Carthusian order, among which eight depicting Carthusian monasteries. All twenty-three of the works still extant are in the Louvre. Research indicates that they were painted on oak panels, with three different types of red oil-based grounds. The three paintings of monasteries which have come through the ages are still on their original supports, whereas the other twenty-two have all been transferred onto canvas. The first transfers were undertaken by J.F. Hacquin c. 1780, using a process which was revealed during the recent restoration work. Information provided by the archvives on interventions on the supports, together with analyses of the grounds used during transfers, enable restoration techniques used during the 19th and 20th centuries to be documented. A second section examines the various stages of the execution of the work. Comparisons between the preparatory drawings which show the squaring, the preliminary stages revealed by X-ray photography and the final stages enable the artistic development to be followed. Important modifications in the composition mainly affect four works, but numerous pentimenti are visible on the X-rays of other paintings and were noted during their restoration. These alterations raise several questions regarding the commission and its execution.